Field of the Invention
The present invention relates to a vibration wave motor, a linear driving apparatus using the vibration wave motor, and an optical apparatus.
Description of the Related Art
In a conventional ultrasonic motor, a high-frequency voltage is applied to a piezoelectric element to ultrasonically vibrate a vibrator fixed to the piezoelectric element. The ultrasonic vibration of the vibrator generates a driving force between a friction member and the vibrator pressed against the friction member. This motor can maintain high output even in a compact size. For example, Japanese Patent Application Laid-Open No. 2012-16107 discloses an ultrasonic motor using a compact vibrator. In addition, various contrivances for the efficient transmission of a driving force to a driving target body have been introduced into the ultrasonic motor. For example, in the ultrasonic motor disclosed in Japanese Patent Application Laid-Open No. 2014-212682, a rolling member is clamped by the resultant force of a pressing force given to the vibrator or its reactive force and the biasing force of a transmission member supported by a driving target body.
In order to downsize and simplify the ultrasonic motor described in Japanese Patent Application Laid-Open No. 2014-212682, there is proposed a sliding structure like that shown in FIG. 11, which is provided with guide shafts 600 extending in the moving direction (the X direction shown in FIG. 11) of a moving member 400, with sliding holes 400a fitted on the guide shafts 600 being formed in the moving member 400. In this sliding structure, the guide shafts 600 and the sliding holes 400a slidably guide the moving member 400. This sliding structure makes it possible to decide a size 400W in the moving direction X of the moving member 400 regardless of the movement amount of the moving member 400, and hence to implement the moving member 400 having the same length as that of the vibrator main body. In addition, since rolling balls can be omitted, the apparatus can be downsized and simplified. In this arrangement, however, the resultant force of the reactive force of the pressing force given to the vibrator and the biasing force of the transmission member supported by the driving target body acts as a drag (in a direction vertical to the drawing surface) on the guide shafts 600 and the sliding holes 400a. This increases the frictional force and decreases the driving force of the ultrasonic motor.